Aftertreatment burner air supply system

ABSTRACT

A system and method for efficient regeneration of a diesel particulate filter used in the exhaust system of a diesel engine, is disclosed. In various systems, a burner is incorporated into the exhaust stream, and prior to the diesel particulate filter. Because the burner requires precise amounts of fuel and air to operate properly, an air flow delivery device, such as a positive displacement pump or blower is incorporated into the system to channel boost air to the burner. Alternatively, a bypass line may be used in conjunction with a pressure regulator, wherein the bypass line diverts the boost air from the pump or blower, while the pressure regulator controls the final pressure to the burner.

TECHNICAL FIELD

The present system and method relate to efficient regeneration of a diesel particulate filter used in the exhaust system of a diesel engine. Specifically, the system and method relate to supplying a burner with precise amounts of fuel and air for properly increasing and maintaining exhaust temperature for efficient filter regeneration.

BACKGROUND

Diesel engines are efficient, durable and economical. Diesel exhaust, however, can harm both the environment and people. To reduce this harm, governments, such as the United States and the European Union, have proposed stricter diesel exhaust emission regulations. These environmental regulations require diesel engines to meet the same pollution emission standards as gasoline engines. Typically, to meet such regulations and standards, diesel engine systems require equipment additions and modifications.

For example, a lean burning engine provides improved fuel efficiency by operating with an amount of oxygen in excess of the amount necessary for complete combustion of the fuel. Such engines are said to run “lean” or on a “lean mixture.” However, the increase in fuel efficiency is offset by the creation of undesirable pollution emissions in the form of nitrogen oxides (NO_(x)). Nitrogen oxide emissions are regulated through regular emission testing requirements. One method used to reduce NO_(x) emissions from lean burn internal combustion engines is known as selective catalytic reduction. When used to reduce NO_(x) emissions from a diesel engine, selective catalytic reduction involves injecting atomized urea into the exhaust stream of the engine in relation to one or more selected engine

Another method for reducing NO_(x) emissions is exhaust gas recirculation (EGR), which is a technique that re-circulates a portion of an engine's exhaust gas back to the engine cylinders. Engines employing EGR recycle part of the engine exhaust back to the engine air intake. The oxygen depleted exhaust gas blends into the fresh air entering the combustion chamber. Reducing the oxygen produces a lower temperature burn, reducing NO_(x) emissions by as much as 50%. The recycled exhaust gas can then be cooled. This “cooled EGR”, can create an even greater reduction in emissions by further lowering the combustion temperatures. When used with a DPF (diesel particle filter), emissions can be reduced up to 90%.

The DPF includes a diesel oxidation catalyst (DOC), which is a ceramic material that heats up in the DPF. Over time, soot and particulate matter accumulates in the DPF, which is cleaned of particulate matter at periodic intervals through a regeneration process. Regeneration is the process of removing the accumulated soot from the filter. This is done either passively (from the engine's exhaust heat in normal operation or by adding a catalyst to the filter) or actively by introducing very high heat (more than 600° C. to burn off the particulate matter) into the exhaust system. The high temperatures need to be maintained continuously from 10 up to 30 minutes for effective regeneration.

Commonly, DPF regeneration systems rely on upstream fuel injection (in-cylinder or in-exhaust) and combustion of the injected fuel in the DOC positioned between the fuel injector and the DPF to create the necessary temperature rise. However, effective DPF regeneration becomes problematic under driving conditions that produce low engine exhaust temperatures, such as observed in stop-and-go traffic. Low temperatures create few opportunities for the DOC to reach the required temperatures needed to initiate and maintain the DPF regeneration. Furthermore, active regeneration events may be interrupted if the temperature at the DOC inlet falls below the required temperature limit (250° C. to 300° C. to burn fuel), making it impossible for the DOC to support the regeneration process. Thus, there is a need for improving the light-off of the DOC during conditions when the exhaust temperature is low and transient.

One method for doing this is to change the engine operation to increase the exhaust temperature. Another method is to add a burner into the exhaust system. If a burner is used, then it needs to be supplied with precise amounts fuel and air to operate properly. Delivering the precise amount of air at the correct pressure can be done by many means, each with their own impact to product cost and engine fuel efficiency.

In an effort the sustain the proper exhaust heat and fuel combustion for effective regeneration, the present system incorporates a burner for heating a portion of the exhaust gas. However, for the burner to operate efficiently, precise amounts of fuel and air must be provided. Delivery of precise amounts of air at the correct volume and pressure can be accomplished by various means, including use of a positive displacement pump device or by use of a pressure increasing device (blower) and a pressure regulator, each option having its own impact on product cost and engine fuel efficiency.

The present system and methods solve these and other problems in providing a system and method for particulate filter regeneration using a burner that is supplied with precise amounts of fuel and air for heating the exhaust stream, thereby providing effective and efficient DPF regeneration.

SUMMARY

A system and method for regenerating a diesel particulate filter, is disclosed. Generally, the system comprises an exhaust system for a diesel engine having a fresh air intake and an exhaust gas output, a burner fluidly connected to the exhaust gas output, a feed line connected to the air intake and the burner, an air flow delivery device such as a positive displacement pump or blower positioned within the feed line, an air flow regulating valve fluidly connected within the feed line for controlling the air flow from the air intake to the burner, and, the particulate filter fluidly connected in the exhaust gas output after the burner.

In another embodiment, the system may also include a pressure regulator within the feed line and the burner. The pressure regulator controls the final pressure to the burner under conditions where the pump is not required. In addition to the pressure regulator, the system may include a bypass line, which diverts air flow around the pump under pressure conditions where the pump is not required. In this embodiment, the system further includes a three-way regulating valve having an inlet for receiving the boost air feed, and a first and second outlet, which are fluidly connected to the bypass line and the pump, respectively, for independent operation.

A method for regenerating a diesel engine particulate filter, is also disclosed. The method comprises the steps of providing an exhaust system for a diesel engine having a fresh air intake stream and an exhaust gas output stream, channeling a portion of the exhaust gas output stream toward a burner connected to the particulate filter, delivering a pre-determined volume of boost air from the fresh air intake stream to the burner, maintaining a pre-determined regeneration temperature of the exhaust gas output stream from the burner to the particulate filter, and, regenerating the particulate filter.

These and other embodiments and their advantages can be more readily understood from a review of the following detailed description and the corresponding appended drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic drawing of an system for regenerating a diesel particulate filter used in an exhaust treatment system of an engine;

FIG. 2 is a schematic drawing of another embodiment of system for regenerating a diesel particulate filter used in the exhaust treatment system of an engine in accordance with the present disclosure; and,

FIG. 3 is a schematic drawing of yet another embodiment of a system for regenerating a diesel particulate filter used in the exhaust treatment system of an engine in accordance with the present disclosure.

DETAILED DESCRIPTION

Generally speaking, and with reference to the engine exhaust system 10 schematic of FIG. 1, a turbocharged, internal combustion engine 12, having a fresh air intake 12 a and an exhaust gas output 12 b, is shown. The engine exhaust system 10 incorporates an exhaust treatment system, including an EGR cooler 14, an turbocharger 16 with a turbocharger compressor 18 and a charge air cooler 20. Such structures will be generally referenced herein and identified in the drawing figures but, as each of these exhaust treatment structures is commonly understood by those skilled in the art, a detailed discussion of the operation of each will not be presented.

The present exhaust treatment system also includes a diesel particulate filter (DPF) 22, which is used to collect particulate matter from the exhaust gas output 12 b. Eventually, the DPF needs to be cleaned or regenerated for effective and continued operation. One method of filter regeneration is to use high temperature exhaust gases. Increasing exhaust temperatures can be accomplished by several means, including adding a burner or burner nozzle 24 to the exhaust system. Because the burner 24 needs to be supplied with precise amounts of fuel and air to operate properly, means have been developed to accomplish providing the necessary air supply. One means includes incorporating air flow/pressure delivery device, such as a positive displacement pump or pressure increasing blower, to the exhaust gas system and in particular, to the air intake. A second means includes incorporating the positive displacement pump or blower and a pressure regulator to the system. The terms “pump” and “blower” are used interchangeable throughout, but it should be understood they relate to an air flow delivery device. The pressure regulator may also be used when the boost air bypasses the pump or blower.

Accordingly, the present system provides for delivering a pre-determined amount of air at the correct pressure to the burner 24 for effective and efficient DPF 22 regeneration, including under conditions of low engine speed and power levels.

With reference to FIG. 1, an embodiment of the exhaust system incorporating a DPF 22, which is proceeded by a burner 24, is shown. The exhaust system 10 incorporates a feed line 30 which is located after the turbocharger compressor 18 in the fresh air intake 12 a. The feed line 30 directs an unregulated boost air feed into the positive displacement pump or blower 26, depending on which is being used, which then directs the desired air flow into the burner 24. The positive displacement pump 26 delivers a specific air flow volume based on a given pump speed. By measuring the pressure and temperature of the unregulated boost air, the pump speed can be calculated and selected to deliver a specific mass flow of air. An engine control unit (ECU) (not shown) may be electronically coupled to and control operation of the positive displacement pump 26, while sensors (not shown) may also be incorporated into system for reading the pressure and temperature of the unregulated boost air, thus working in conjunction with the ECU for operation of the pump. For further pressure and flow control, an air flow regulating valve or check valve 32 is fluidly connected within the feed line 30 for controlling the air flow through the feed line to the burner 24. The check valve may also be controlled through the ECU.

With reference to FIG. 2, another embodiment of the system is shown incorporating a positive displacement pump or blower 26, a bypass line 34 and a pressure regulator 36. When the air boost pressure is higher than the burner pressure requirement, it may be advantageous to control the pressure of the air being generated from the positive displacement pump or blower 26. In this instance, a pressure regulator 36 can be installed within the feed line 30 between the positive displacement pump or blower 26 and the burner 24. The pressure regulator 36 in conjunction with the check valve 32, controls the air flow and pressure to the burner 24. The burner 24 can then operate properly to increase the exhaust gas temperature to levels required for effective DPF 22 regeneration.

Alternatively, rather than having the boost air flow through the pump 26, the bypass line 34 may be activated. The bypass line 34 diverts the air flow around the pump 26 if the boost air pressure is at a level high enough to meet the burner pressure requirement without the need to activate the pump. Controlling whether the boost air flows through the pump 26 or the bypass line 34 can be accomplished through operation of a regulating device, such as a three-way regulating valve 38 incorporated into the feed line 30. The regulating valve 38 includes an inlet 38 a and a first and second outlets 38 b, 38 c, wherein the inlet and outlets are fluidly connected to the feed line 30. In one embodiment, the bypass line 34 is fluidly connected to the first outlet 38 b, while the pump 26 is connected to the second outlet 38 c of the three-way regulating valve 38. The arrangement of the regulating valve 38, pump 26 and bypass line 34 can vary depending on the engine and exhaust system requirements. Operation of the regulating valve 38 may be controlled by real-time signals from the ECU (not shown). Signals for the regulating valve 38 are based on pressure and air flow readings of the boost air. Sensors (not shown), either temperature or pressure, are used to feed information to the ECU about the characteristics of the air flow, which in turn operates the regulating valve 38 to either send boost air through the bypass line 34 or the pump or blower.

In many instances, the air requirement of the burner 24 is approximately 10% of the total engine air flow requirement. However, at low engine speed and power levels, such as during stop-and-go driving conditions, the pump or blower 26 is required to supply the burner 24 with the necessary air flow and pressure to heat the exhaust gas stream to regenerate the DPF 22. Any extra air drawn into the pump or blower 26 requires matching through the turbocharger 16. Therefore, when using the pump or blower, it may be advantageous to draw the boost air directly from the fresh air intake 12 a so the turbocharger 16 and turbocharger compressor 18 are not affected. Alternatively, there may be enough boost air pressure to supply the burner 24 using a bypass line, without requiring a pump or blower, as previously discussed. Operation of the pump or blower may be controlled by real-time signals from the ECU (not shown), as previously discussed.

FIG. 3 illustrates an embodiment where the fresh boost air can be drawn before it reaches the turbocharger compressor 18 or alternatively, after the turbocharger compressor. In this embodiment, there are two separate feed lines, a first feed line 40 connected directly to the fresh air intake 12 a and leading to the positive displacement pump or blower 26. There is also a first air flow regulating valve 44, which regulates the air flow from the pump or blower 26 to the main feed line 30 and ultimately to the burner 24. This arrangement would be useful in particular during conditions of low engine speeds and power levels, when extra air is required to feed the burner 24. This embodiment is advantageous in that the boost air is taken directly from the air intake 12 a and before it reaches the turbocharger compressor 18, thus mitigating the affect on the turbocharger. The air is then channeled through the pressure regulator 36, and ultimately to the burner 24.

In another embodiment, also shown in FIG. 3, there is a second feed line 42 connected after the turbocharger compressor 18. This feed line 42 also includes a second air flow regulating valve 46, which regulates the boost air flow to the main feed line 30, through the pressure regulator 36 and to the burner 24. This arrangement is similar to the embodiment of FIG. 2. Because a pump or blower is not used in this arrangement, the pressure regulator 36 controls the final air pressure to the burner 24. This arrangement is useful during periods of full engine speeds and power levels. 

What is claimed is:
 1. A system for regenerating a diesel particulate filter, the system comprising: an exhaust system for a diesel engine having a fresh air intake and an exhaust gas output; a burner fluidly connected to the exhaust gas output; a feed line connected to the air intake and the burner; a positive displacement pump positioned within the feed line; an air flow regulating valve fluidly connected within the feed line for controlling the air flow from the air intake to the burner; and, the particulate filter fluidly connected in the exhaust gas output after the burner.
 2. The system of claim 1, wherein the fresh air intake provides air to the exhaust system and the feed line.
 3. The system of claim 2, wherein the fresh air intake provides an unregulated boost air stream to the positive displacement pump.
 4. The system of claim 1, wherein the positive displacement pump is positioned before the air flow regulating valve within the feed line.
 5. The system of claim 4, wherein the pump delivers a pre-determined air flow to the burner.
 6. The system of claim 1, wherein the air flow regulating valve is a check valve.
 7. The system of claim 1, wherein the system further includes a three-way regulating valve positioned within the feed line, the valve having an inlet and a first and second outlet.
 8. The system of claim 7, wherein the system further includes a bypass line fluidly connected to the first outlet of the three-way regulating valve.
 9. The system of claim 7, wherein the pump is connected within the feed line to the second outlet of the three-way regulating valve.
 10. The system of claim 9, wherein the bypass line diverts air flow around the pump to the air flow regulating valve and the burner.
 11. The system of claim 1, wherein the system further includes a pressure regulator positioned within the feed line before the burner.
 12. A system for regenerating a diesel particulate filter, the system comprising: an exhaust system for a diesel engine having a fresh air intake and an exhaust gas output; a burner fluidly connected to the exhaust gas output; a feed line connected to the air intake and the burner; a three-way regulating valve having an inlet and a first and second outlet, wherein the inlet and outlets are fluidly connected to the feed line; an air flow delivery device positioned within the feed line at the first outlet of the regulating valve; a bypass line positioned within the feed line at the second outlet of the regulating valve; a pressure regulator fluidly connected within the feed line for controlling the air flow from one of the bypass line and the air flow device to the burner; and, the particulate filter fluidly connected in the exhaust gas output after the burner.
 13. A system for regenerating a diesel particulate filter, the system comprising: an exhaust system for a diesel engine having a fresh air intake connected through a turbocharger compressor, and an exhaust gas output; a burner fluidly connected to the exhaust gas output; a first feed line connected to directly to the air intake; an air flow delivery device within the first feed line; a first air flow regulating valve fluidly connected within the first feed line for controlling the air flow from the air intake to the positive displacement pump to the burner; a second feed line connected to the air intake after the turbocharger compressor; a second air flow regulating valve fluidly connected within the second feed line for controlling the air flow from the air intake to a pressure regulator and the burner; and, the particulate filter fluidly connected in the exhaust gas output after the burner.
 14. The system of claim 13, wherein the system further includes an electronic control module for activating either one of the first air flow valve and the second air flow valve for delivering a pre-determined air flow to the burner.
 15. The system of claim 13, wherein the system further includes a pressure regulator positioned before the burner.
 16. The system of claim 13, wherein the air flow delivery device is one of a positive displacement pump and a blower.
 17. A method for regenerating a diesel engine particulate filter, the method comprising the steps of: providing an exhaust system for a diesel engine having a fresh air intake stream and an exhaust gas output stream; channeling a portion of the exhaust gas output stream toward a burner connected to the particulate filter; delivering a pre-determined volume of boost air from the fresh air intake stream to the burner; maintaining a pre-determined regeneration temperature of the exhaust gas output stream from the burner to the particulate filter; and, regenerating the particulate filter.
 18. The method of claim 17, wherein the step of delivering the volume of boost air includes delivery through a feed line connecting the fresh air intake stream to the burner.
 19. The method of claim 18, wherein the step of delivering the volume of boost air further includes adding at least one air flow regulating valve to the feed line.
 20. The method of claim 17, wherein the step of regulating the pressure of the booster air to the burner includes providing an air flow delivery device within the feed line.
 21. The method of claim 20, wherein the step of regulating the pressure of the booster air includes providing a pressure regulator between the burner and the air flow delivery device.
 22. The method of claim 17, wherein the step of regulating the pressure of the booster air to the burner includes providing a pressure increasing device.
 23. The method of claim 22, wherein the pressure increasing device includes a blower.
 24. A system for regenerating a diesel particulate filter, the system comprising: an exhaust system for a diesel engine having a fresh air intake and an exhaust gas output; a burner fluidly connected to the exhaust gas output; a feed line connected to the air intake and the burner; a means for delivering a pre-determined amount of air from the fresh air intake into the feed line; an air flow regulating valve fluidly connected within the feed line for controlling the air flow from the air intake to the burner; and, the particulate filter fluidly connected in the exhaust gas output after the burner.
 25. The system of claim 24, wherein the means for delivering the pre-determined amount of air includes a positive displacement pump.
 26. The system of claim 24, wherein the means for delivering the pre-determined amount of air includes a pressure increasing blower. 